1. Field of the Invention
The present invention relates to an image carrier unit including an image carrier capable of carrying an electrostatic image and image forming apparatus including the image carrier unit.
2. Description of the Related Art
There is widely used such an image forming apparatus configured to transfer a toner image formed on an image carrier to a sheet directly or through an intermediary of an intermediate transfer body and to fix the image to the sheet by heating and pressing the sheet to which the toner image has been transferred. In general, a photoconductive drum which is one exemplary image carrier is supplied to a user in a form of a process cartridge which is one exemplary image carrier unit. The process cartridge is configured such that a charging device, a developing device and others are built into a cartridge casing together with the photoconductive drum and to be able to replace them in a body.
Japanese Patent Application Laid-open Nos. 2004-170556 and 2009-75274 disclose an image forming apparatus in which a plurality of process cartridges is arrayed along an intermediate transfer belt. The plurality of process cartridges is configured to be able to be attached and to be replaced individually to/from a casing of the image forming apparatus by being moved in a rotational axis direction of the photoconductive drum.
The process cartridge disclosed in Japanese Patent Application Laid-open No. 2004-170556 is provided with an opening for making the photoconductive drum come into contact with the intermediate transfer belt and with a protection cover of the photoconductive drum for covering the opening. The protection cover prevents the photoconductive drum from being irradiated by light or from collecting dusts during processes of shipping and storage of the process cartridge. The protection cover engages with first and second engage portions disposed at both sides of the opening of a cartridge casing and is held to be able to move in the rotational axis direction of the photoconductive drum.
As shown in FIG. 10A, a direction in which the engagement at a first engagement mechanism (71L, 72L) becomes shallow is opposite from a direction in which the engagement at a second engagement mechanism (71R and 72R) becomes shallow. Due to that, if the protection cover (10) is strongly pulled in a direction distant from the photoconductive drum 1Bk (upward) as shown in FIG. 10B, the protection cover deforms inwardly, the engagements of the first and second engagement mechanisms become shallow in the same time, and there is a possibility that the protection cover comes off from the process cartridge.
A drum cartridge disclosed in Japanese Patent Application Laid-open No. 2009-75274 is configured such that a protection cover abuts against a casing of an image forming apparatus and is automatically removed such that it is pushed out of a drum cartridge in attaching the drum cartridge to the casing of the image forming apparatus by moving the drum cartridge in a rotation axis direction of the photoconductive drum.
Because such a protection cover is so large as to cover an entire process cartridge, it is not preferable to use an excessive material as a protection cover attached only during a period from a packing state until when the process cartridge is attached to the image forming apparatus. If the whole process cartridge including the protection cover is large, it is troublesome during shipping, storage and handling.